An integrated circuit commonly includes a core portion and an input-output (I/O) portion. The I/O portion functions for circuits in the core portion to interface with circuits outside of the integrated circuit. Core transistors in the core portion operate at a voltage lower than that of I/O transistors in the I/O portion. As newer technology nodes are introduced approximately every 18 to 36 months, the maximum safe operating voltage of core transistors is lowered. However, between different technology nodes, operating voltages for I/O transistors change less often than the maximum safe operating voltage of core transistors. In various approaches, multiple gate oxides are used for I/O transistors to meet I/O specifications for newer technology nodes. In other approaches, special transistors are used to overcome the discrepancy between I/O voltages and safe operating voltages for core transistors. These special transistors commonly have a higher safe operating range to meet the I/O specifications. Drain extended Metal-Oxide Semiconductor (MOS), Complementary MOS (CMOS) and Double Diffused MOS (DMOS), Bipolar CMOS-DMOS (BCDs) transistors are examples of special transistors. With the advent of Fin Field-Effect-Transistors (FinFETs), special transistors may not meet the I/O requirements.
Like reference symbols in the various drawings indicate like elements.